The subject invention relates to aqueous coating compositions. More particularly, the invention relates to aqueous coating compositions especially useful for the filling of wood.
The customary procedure in the finishing of wood surfaces, e.g., furniture, millwork, panelling, etc. with a clear topcoat involves first the application of an optional sealer coat and a filler coat. The sealer coat, if applied, seals the wood and provides a base for the filler coat. The primary function of the filler coat is to fill the grooves and other surface imperfections found in wood. Once filled, the coated wood product is sanded so as to give it a smooth surface. Thus, subsequent application to the wood of a topcoat and/or print coat is to a substantially flat surface.
Filler coats must have the ability of drying quickly to a hard surface so as to facilitate a subsequent sanding step and preferably be applied in one pass so as to minimize handling. The problem of applying a filler coat in one pass is especially difficult with respect to low grade wood. Low grade woods, such as lauan, have deep grooves which must be filled. Accordingly, any filler which is to be applied in one pass must have a shear viscosity low enough that it is able to fill the groove, yet a yield point high enough that the coating bridges the groove and does not itself contract upon drying. Many different types of filler coating compositions are known. However, as above indicated, there is still a need for a filler composition which has a rheology which allows it to be applied in a conventional manner to low grade wood. Preferably, the application of the filler could be done in one pass.
It is also described that the filler coating composition be water-based. Many organic solvent-based coating compositions are known. However, the organic solvents themselves are costly. Additionally, equipment must be installed so as to remove the solvent from the atmosphere following its application and evaporation from the coated substrate. Water, of course, is cheap and does not have an inherent pollution problem.
There have now been found filler coating compositions which are capable of application in one pass to low grade wood. The coating compositions additionally are water-base and storage stable over a prolonged period of time.
As used herein, all percentages and ratios are by weight unless otherwise indicated.